a. Briefly explain the advantages and disadvantages of HVDC transmission.

b. A DC-link has a loop resistance of 5Ω and is connected to transformers giving secondary voltage of 110kV at each end. The bridge connected converters operate as follows. Rectifier: ????= 150,????= 10Ω Inverter: ????0= 100,????= 150,????=10Ω Allow 50 margin on ????0 for ????: Calculate the direct current delivered if the inverter operates on constant ???? control. 

c. Table 02is a re-production of a part of typical interruption data from a power utility for its feeder circuits. Feeder 7075 serves 1,500 customers with a total load of 5 MW. Excluding momentary interruption events and major events, which are omitted from Table 01, calculate the SAIFI, SAIDI, CAIDI, and ASAI for this feeder.

Table 02: Interruption Data

Outage data	Time at beginning of outages	Outage duration (minutes)	Feeder	Number of customers interrupted
17/1/2018	12:12:56	8.17	7075	200
5/2/2018	00:23:10	71.3	7075	600
6/3/2018	09:30:10	23.5	7072	25
8/3/2018	01:13:00	30.3	7075	90
15/3/2018	08:55:23	12.4	7075	500
23/4/2018	21:20:14	267.2	7075	60
12/5/2018	08:20:02	86.4	7072	70
13/5/2018	15:45:39	110	7075	700
6/8/2018	10:11:10	42.3	7075	120
20/9/2018	10:15:56	100.6	7072	750
21/10/2018	18:20:10	10.8	7075	300
23/10/2018	18:00:40	40.5	7075	100
4/11/2018	03:45:50	23.7	7072	360
22/11/2018	06:10:33	25.6	7075	100

d. What do you mean by “Smart Grid”? Explain the concept covering the main features.